HSC Survey Results

German Bank Survey # 2 Results from 18/08/2024

Survey Details

6 commercial purse seiners conducted this fishing survey on 18/08/2024 starting at 20:00:00.

All vessels ran two transects in the German Bank box and two transect in the Seal Island Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Melissa.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for German Bank using standardized parallel transects is 14,054mt, and with turnover applied 11,668mt. The preliminary biomass estimate for Seal Island is 6,285mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2024-08-18 19:43:44 2024-08-18 22:03:05 -66.493 43.560 -66.493 43.237 GB 36.06 8.38
BP T02 2024-08-18 22:42:29 2024-08-19 01:01:56 -66.357 43.235 -66.357 43.560 GB 36.17 8.40
BP T03 2024-08-19 01:38:10 2024-08-19 03:16:11 -66.230 43.501 -66.233 43.245 GB 28.47 9.41
BP T04 2024-08-19 03:32:26 2024-08-19 05:23:01 -66.178 43.247 -66.179 43.502 GB 28.37 8.31
FM T01 2024-08-18 20:56:47 2024-08-18 23:24:05 -66.424 43.565 -66.424 43.234 GB 38.26 8.42
FM T02 2024-08-19 00:07:58 2024-08-19 02:30:34 -66.284 43.242 -66.285 43.565 GB 36.92 8.39
FM T03 2024-08-19 02:59:21 2024-08-19 04:45:05 -66.203 43.501 -66.201 43.246 GB 29.63 9.08
FM T04 2024-08-19 05:00:51 2024-08-19 06:42:16 -66.144 43.249 -66.144 43.500 GB 29.04 9.28
LB T01 2024-08-18 19:49:58 2024-08-18 22:35:35 -66.448 43.565 -66.447 43.233 GB 38.44 7.52
LB T02 2024-08-18 23:19:33 2024-08-19 01:47:02 -66.309 43.233 -66.309 43.566 GB 37.94 8.33
LB T03 2024-08-19 02:20:38 2024-08-19 04:01:55 -66.210 43.501 -66.211 43.247 GB 29.06 9.30
LB T04 2024-08-19 04:20:49 2024-08-19 06:10:30 -66.154 43.250 -66.154 43.502 GB 28.98 8.56
LJ T01 2024-08-18 20:17:46 2024-08-18 22:43:20 -66.470 43.567 -66.470 43.233 GB 37.18 8.28
LJ T02 2024-08-18 23:22:24 2024-08-19 01:41:09 -66.332 43.234 -66.332 43.565 GB 36.89 8.61
LJ T03 2024-08-19 02:17:03 2024-08-19 03:59:16 -66.221 43.501 -66.220 43.247 GB 28.23 8.95
LJ T04 2024-08-19 04:14:46 2024-08-19 06:05:23 -66.164 43.247 -66.163 43.505 GB 28.80 8.44
LM T01 2024-08-18 19:36:54 2024-08-18 22:04:21 -66.378 43.568 -66.379 43.236 GB 37.80 8.30
LM T02 2024-08-18 22:40:06 2024-08-19 01:04:34 -66.241 43.232 -66.240 43.566 GB 37.65 8.44
LM T03 2024-08-19 01:29:54 2024-08-19 03:18:07 -66.182 43.500 -66.183 43.248 GB 28.77 8.61
LM T04 2024-08-19 03:33:47 2024-08-19 05:23:34 -66.125 43.246 -66.126 43.503 GB 29.10 8.59
MS T01 2024-08-18 19:41:45 2024-08-18 22:32:17 -66.401 43.566 -66.401 43.234 GB 39.90 7.58
MS T02 2024-08-18 23:16:13 2024-08-19 01:37:04 -66.263 43.236 -66.263 43.566 GB 38.51 8.86
MS T03 2024-08-19 02:07:13 2024-08-19 03:49:31 -66.191 43.500 -66.192 43.248 GB 30.02 9.51
MS T04 2024-08-19 04:07:46 2024-08-19 05:59:59 -66.136 43.250 -66.135 43.504 GB 31.00 8.95

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
FM T04 -35.5 -47.366 0.065
MS T04 -35.5 -47.458 0.064
LM T04 -35.5 -47.985 0.056
FM T01 -35.5 -49.571 0.039
LB T04 -35.5 -50.613 0.031
FM T02 -35.5 -51.273 0.026
LB T02 -35.5 -52.056 0.022
MS T02 -35.5 -52.199 0.021
MS T01 -35.5 -53.197 0.017
BP T01 -35.5 -53.478 0.016
LM T01 -35.5 -53.549 0.016
LJ T01 -35.5 -53.803 0.015
LB T01 -35.5 -54.430 0.013
BP T02 -35.5 -55.154 0.011
LJ T04 -35.5 -55.430 0.010
FM T03 -35.5 -56.537 0.008
LB T03 -35.5 -57.075 0.007
BP T04 -35.5 -57.108 0.007
LJ T02 -35.5 -57.764 0.006
LM T02 -35.5 -58.321 0.005
LM T03 -35.5 -58.539 0.005
MS T03 -35.5 -60.622 0.003
LJ T03 -35.5 -63.033 0.002
BP T03 -35.5 -63.535 0.002
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
German Bank -35.5 810.6554 -53.1105 0.0173 14,054 73.9 69.1 2,174.69 15.47
Seal Island -35.5 287.0035 -52.0955 0.0216 6,285 26.1 30.9 2,108.41 33.54

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by LM, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by FM, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
German Bank 1 2024-08-04 12,233 12,233 2023-08-06 2,687 2,687 2,021 2,021
Seal Island 1 2024-08-04 45,930 NA 2023-08-06 1,205 NA 929 NA
German Bank 2 2024-08-18 14,054 11,668 2023-08-20 4,930 4,406 3,282 2,887
Seal Island 2 2024-08-18 6,285 NA 2023-08-20 1,918 NA 897 NA
German Bank 3 NA NA NA 2023-09-03 9,959 8,901 8,372 7,660
German Bank 4 NA NA NA 2023-09-13 16,266 13,203 15,011 12,498
Seal Island 3 NA NA NA 2023-09-03 2,063 NA 1,099 NA
Seal Island 4 NA NA NA 2023-09-13 5,636 NA 4,045 NA
German Bank 5 NA NA NA 2023-09-27 15,242 11,360 13,503 9,978
Seal Island 5 NA NA NA 2023-09-27 53,844 NA 42,269 NA
German Bank 6 NA NA NA 2023-10-11 23,614 20,057 26,563 23,390
Seal Island 6 NA NA NA 2023-10-11 15,261 NA 14,381 NA
German Bank 7 NA NA NA 2023-10-24 11,184 5,502 13,033 6,803
Seal Island 7 NA NA NA 2023-10-24 1,006 NA 1,087 NA
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 German Bank 83,882 66,116 81,785 65,237
2023 Seal Island 80,933 NA 64,707 NA
2024 German Bank 26,287 23,901 NA NA
2024 Seal Island 52,215 NA NA NA

Tagging, Plankton, and CTD Data

Summary map

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Melissa Lady Melissa
Set Number GB2024-03 GB2024-04
Ground GB GB
Date 18/08/2024 18/08/2024
Wind Direction (km/h) NE NE
Swell (m) 2 2
Air Temp (c) 24 24
Tow Details
Tow Start 18:58:00 19:15:00
Tow End 19:08:00 19:25:00
Start Lat 43.57067 43.56367
End Lat 43.56183 43.58317
Start Lon -66.35800 -66.36067
End Lon -66.35733 -66.36750
Avg Tow Depth (m) 6.186492 9.133168
Speed 3.3 6.8
Heading 120 347
Tide Direction against with
Other Data Collection
Flow Start 435080 478545
Flow End 478545 544511
No. Revolutions 43465 65966
Distance (m) 1168.035 1772.704
Volume 3669.382 5568.951
Secchi Disappear (m) 7 7
Secchi Reappear (m) 6 6

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is GB2024-03, which was against the tide and had an average depth of 6.1864922m. The second tow is GB2024-04, which was with the tide and had an average depth of 9.133168m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 German Bank surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for German Bank.

Vessel Performance

Speed

Average vessel speed was 8.6. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.